This relates generally to integrated circuits, and more particularly, integrated circuits with imager pixels that include gapless microlens arrays.
Modern electronic devices such as cellular telephones, cameras, and computers often use digital image sensors. Imagers (i.e., image sensors) may be formed from a two-dimensional array of image sensing pixels. Each pixel receives incident photons (light) and converts the photons into electrical signals.
Modern imagers are sometimes formed with a gap-less microlens array. The gap-less microlens array is used to focus incident light on the pixels of the array of image sensing pixels. Conventional reflowed gap-less microlens arrays are formed in two separate groups. Each group of microlenses is formed in a separate layer (e.g., as part of a separate integrated circuit fabrication step). The first group of microlenses is deposited and formed with reflow processes (e.g., using photolithographic processes, the first group of microlenses are deposited and then melted into their final shape). After the first group of lenses is formed, the second group of microlenses is deposited and formed with similar processes.
In gapless microlens arrays, it is necessary to form the second set of microlenses such that the second set of microlenses approximately vertically overlaps the first set of microlenses. However, during the process of forming the second set of microlens structures, the second set of microlens structures often become misaligned with the first set of microlens structures. Misalignment of the microlens structures may cause undesired effects such as crosstalk between pixels, reduced incident light conversion efficiency, increased noise, and problems with color shading.
It would therefore be desirable to provide gap-less micro-lens arrays with improved alignment.